Australia captain Michael Clarke said his side had it in them to complete one of the great Ashes comebacks after England ended the fourth day of the first Test poised for victory.

The tourists were 174 for six at Trent Bridge come Saturday's close, still needing a further 137 runs on Sunday's final day with just four wickets standing to go 1-0 up in this five-match series against Ashes-holders England.

Shortly before stumps, Australia lost three wickets for three runs with Clarke's exit for 23 sparking the slump.

However, teenage debutant Ashton Agar was still there on one not out after being promoted from last man to No 8 following his first innings 98 -- the highest score by a Test No 11.

"Ashton showed in the first innings he's got plenty of talent and with the experience of Brad Haddin (11 not out) and the other players that are left to bat, I think we can give it a real shake," said Clarke.

Clarke is just one of three survivors, along with England's Kevin Pietersen and Ian Bell, from the celebrated 2005 Ashes Test at Edgbaston when Australia, who ended the third day on 175 for eight chasing 282, got within a hit of victory before England squeezed home by two runs.

"We're still a fair way away but I think the way we've seen the roller coaster of Test cricket go up and down for the past four days, anything is possible on Sunday," Clarke said.

This match, as well as producing some enthralling cricket, has also been bedevilled by several umpiring controversies.

The latest concerned Clarke's exit on Saturday when, after the third umpire confirmed he'd been caught cleanly by wicketkeeper Matt Prior off Stuart Broad, the star batsman still called for a review.

Hot Spot technology indicated Clarke had nicked the ball and his move meant Australia had used up all their reviews -- something that could yet prove costly on Sunday.

"I knew I had hit my pad. I asked my partner (Steven Smith) and he certainly wasn't convinced I hit it either so I referred it," said Clarke.

"Then I was given out and had another look when I came in the change room and there was a little spot there on Hot Spot. That's how the review system operates."

There was a major flash point Friday when Broad, on 37, got a huge edge off 19-year-old left-arm spinner Agar that was caught by Clarke at slip.

However, experienced Pakistani umpire Aleem Dar gave Broad not out and, as Australia had used up their reviews, the tourists had to accept the decision.

Broad went on to make 65 and helped Bell, who struck a masterful 109, add a potentially match-turning 138 for the seventh wicket.

"We would've liked him out for a lot less that's for sure, but that's the way the game goes," said Clarke. "I'm not going to go back there. Sometimes you get away with it, sometimes you don't."

Prior to this match, England had never lost a Test in which Bell had scored a hundred and the 31-year-old's 18th century in 89 fixtures at this level certainly put them in the box seat.

"I think it's certainly my best Ashes innings," said Bell. "It was nice to put an innings together when the team needed it most."

However, he added: "I've played too much Ashes cricket to take anything for granted."

Memories of Edgbaston 2005 were still vivid for Warwickshire right-hander Bell, who said: "It was my home ground, a game I'll never forget but hopefully it doesn't get that tight tomorrow."

When cricket lovers wake on Thursday, they will be consumed with excitement. A concoction of nerves, energy and enthusiasm overcome in readiness for the first day of the Australian Test summer. For Australian and English supporters, there is extra emotion attached for an Ashes series.

Australia captain Michael Clarke was a relieved man after hitting his 8th ODI century in an 88-run win over England at Old Trafford as he played a key role in his first victory over a Test nation in seven months.